In recent years, a CMOS (Complementary Metal Oxide Semiconductor) image sensor is widely used as a (solid-state) image pickup device from the point of view of the cost and so forth.
In the CMOS image sensor, a slope type AD conversion circuit is widely utilized for AD (Analog to Digital) conversion of an electric signal outputted from a pixel (hereinafter referred to also as pixel signal). In the slope type AD conversion circuit, a ramp signal is used as a reference signal (voltage) and the reference signal and the pixel signal are compared with each other by a comparator, and a time period before an output of the comparator reverses is counted by a counter to perform AD conversion of the pixel signal (for example, refer to PTL 1).
According to the slope type AD conversion circuit, a column AD conversion circuit can be configured in which, for example, a slope type AD conversion circuit is arrayed for each pixel column and the AD conversion is performed at the same time for all columns.